In general, a mobile terminal (e.g., a cell phone or a Personal Digital Assistant (PDA)) is a device for providing a communication function by which a user can make a call or exchange data while moving. The mobile terminal recently has been regarded as a personal necessity of modern life for people of all ages and both sexes, and a demand on the mobile terminal is expected to increase. With the development of technologies of the mobile terminal, various menus are provided so that a user can operate the mobile terminal by directly setting a bell sound type, a bell sound volume, an alarm, a lock, a transmission/reception restriction, and the like.
Meanwhile, although mobile terminals have slightly different forms, all of the mobile terminals have a locking function to prohibit other users against unauthorized use of a specific function or against reading of stored data. Examples of the locking function include automatic locking for prohibiting all usages of a mobile terminal, international call locking for restricting outgoing international calls, privacy protection locking for restricting checking of a stored phone number or an incoming/outgoing phone number or a message. The locking function is not limited to the above examples, and thus can be assigned to all functions which require avoidance of unauthorized use of other users.
In the conventional technique, a user combines several numeric characters by using a plurality of key buttons to pre-register a password of the user to a terminal, and sets a locking function by selecting a function to be restricted. Once the locking function is set, the user can unset the locking function of a specific function by inputting the pre-registered password. However, since the conventional terminal has pursued compact in size and light in weight according to its characteristic, a keypad needs to be configured such that a size of a keyboard layout or the number of keys thereof have a basic form capable of inputting minimum content. Therefore, there is a limitation in a format of a password that can be registered by the user. Additionally, the aforementioned method of registering a password by combining a plurality of numeric characters has a problem in that the password can be easily guessed by other users since personal information (e.g., a birthday, an anniversary, a social security number, and so forth) is used as the password in many cases.
Accordingly, there is a need for a method capable of overcoming a problem of the conventional technique in which a locking function of a terminal is restricted and capable of increasing security of the locking function.